(Ehrenberg) Mills 1935
Tetracyclus emarginatus has slightly undulate and concave margins, while T. glans has rounded, convex margins. Tetracyclus rupestris valves are elliptic to circular, with a broad axial area.
Bishop and Spaulding 2015
(Braun ex Rabenh.) Grunow in Van Heurck 1885
(Ehrenb.) W.Sm.